EP1882769B1

EP1882769B1 - Laundry machine with a motion sensor

Info

Publication number: EP1882769B1
Application number: EP06117834A
Authority: EP
Inventors: Stefano Galassi
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2006-07-25
Filing date: 2006-07-25
Publication date: 2011-09-07
Anticipated expiration: 2026-07-25
Also published as: WO2008012032A1; ATE523623T1; EP1882769A1; RU2009106465A; PL1882769T3; ES2373325T3

Abstract

A laundry machine (1) having: a casing (2) resting on a floor (3) on a number of feet (4); a revolving drum (5) supported by the casing (2); a control unit (14) implementing a method of analysing machine vibration; and at least one motion sensor (16) connected to the control unit (14) and located close to one foot (4).

Description

TECHNICAL FIELD

The present invention relates to a laundry machine with a motion sensor.
The present invention may be used to particular advantage in a washing machine, to which the following description refers purely by way of example.

BACKGROUND ART

When a washing machine rests on a flexible floor (e.g. a wooden floor, a soft floor, or a floor resting on a thin slab), the vibration generated by the washing machine (especially during the spin cycle) may be resonance-amplified to an unacceptable noise level.
To reduce vibration of a washing machine, it is important to avoid rotating the drum at operating rotation speeds close to those at which resonance phenomena occur. Since the drum rotation speeds at which resonance phenomena occur mainly depend, however, on installation conditions, and in particular on the type of floor, optimum drum rotation speed varies from one machine to another and from one installation to another, so that it is practically impossible to determine beforehand, at the manufacturing stage, the rotation speeds at which resonance phenomena occur and which are therefore to be avoided.
As a result, it is not enough to set the washing machine controls to spin the drum (defining the wash tub) at given rotation speeds, and the optimum rotation speeds of the drum must be determined at each spin cycle to minimize machine vibration. US5930855A1 describes a method of optimizing the rotation speed of a washing machine drum to minimize vibration of the machine: the washing machine employs an accelerometer mounted close to the top of the casing to sense machine vibration, and a computer software program monitors, records, and compares machine vibrations over a range of rotation speeds to determine a rotation speed which minimizes machine vibration.
Tests show that, in known washing machines of the type disclosed in US5930855A1 , machine vibration sensing is not always entirely satisfactory, so that the rotation speeds minimizing machine vibration may not be determined as accurately as expected.
US 2004/0154351 discloses a vibration sensing assembly for sensing the vibration of the tub with respect to the casing and including a fixing part fixed to an inner wall of the cabinet, a rotational part rotatable connected to the fixing part to perform a rotational movement within a predetermined range by the vibration of the tub centering around a portion connected to the fixing part, and a sensor provided to the rotational part to sense the rotational movement of the rotational part.
GB 1 146 664 discloses a sensor device, which is disposed at, or adjacent to, a suitable location within the appliance which is sensitive to the vibrational movement during operation thereof. The device includes a piezoelectric crystal, which generates a voltage signal indicative of the amplitude of the vibrational movement. If the monitored amplitude exceeds a predetermined threshold value, thereby indicating that the machine is being subjected to excessive vibrational movement, a microprocessor causes the machine to go into a re-distribute mode to attempt to re-distribute the uneven load of the machine.
DE 10 2004 049 647 discloses a method of monitoring a washing machine aggregate for impermissible or atypical movements during a first phase of a washing program while water is being filled into the aggregate and for discontinuing the filling upon detection of such movement as may result, for instance, from the presence of a child or animal in the aggregate.
EP 1 167 609 discloses accelerometers or optical means which are directed along a direction that is sensitive to the effect of a load which is dynamically unbalanced, the direction being parallel to the axis of rotation of the drum.
BE 1 010 008 disclose a method for determining residual moisture during a drying process, more specifically for drying linen, whereby the drying process is regulated in accordance with the desired residual moisture, a specific feature being that the residual moisture is determined by means of a measurement of the quantity of water present in the linen.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a laundry machine with a motion sensor, designed to eliminate the aforementioned drawbacks, and which is cheap and easy to implement.
According to the present invention, there is provided a laundry machine with a motion sensor, as claimed in the accompanying Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a schematic side view of a washing machine in accordance with the present invention;
Figure 2 shows a schematic side view of a portion of an alternative embodiment of the Figure 1 washing machine; and
Figure 3 shows a schematic side view of a portion of a further embodiment of the Figure 1 washing machine.

PREFERRED EMBODIMENTS OF THE INVENTION

Number 1 in Figure 1 indicates as a whole a washing machine comprising a casing 2 resting on a floor 3 on a number of feet 4. Casing 2 supports a revolving drum 5 (defining a wash tub) which rotates about a horizontal rotation axis 6 (in alternative embodiments not shown, rotation axis 6 may be tilted or vertical), and front access to which is closed by a door 7 hinged to casing 2.
Drum 5 is rotated about rotation axis 6 by an electric motor 8 connected to drum 5 by a transmission system, which comprises a belt 9 connecting a pulley 10, fitted to the shaft of drum 5, directly to a pulley 11 fitted to the shaft of electric motor 8. In an alternative embodiment not shown, electric motor 8 is coaxial with drum 5, and the shaft of drum 5 is connected rigidly to the shaft of electric motor 8.
Electric motor 8 is equipped with a drive system 12; and a tachometer generator 13 (or other equivalent speed-sensing device) for measuring the speed of electric motor 8 and therefore the rotation speed of drum 5. Drive system 12 of the motor is preferably operated on the basis of the difference between the command (desired) speed and the actual speed as read by tachometer generator 13.
Washing machine 1 also comprises a control unit 14, which receives user commands from a user interface 15, and controls overall operation of washing machine 1. Control unit 14 is connected to at least one machine vibration-sensing accelerometer 16. In an alternative embodiment not shown, vibration-sensing accelerometer 16 is replaced by a different type of motion sensor.
Control unit 14 implements a known method of analysing machine vibration to determine the rotation speeds at which machine vibration is maximum and/or minimum and so identify the rotation speeds at which resonance phenomena occur. During normal use, drum 5 is obviously rotated at different speeds from those at which resonance phenomena occur. The method of determining the rotation speeds at which machine vibration is maximum and/or minimum may be performed only once, after the washing machine is actually installed, may be performed at given periods, or may be performed at each cycle.
According to the present invention, accelerometer 16 is located close to a foot 4 and therefore close to floor 3. Various tests and analyses show this to be the most effective position for high-precision sensing the most dangerous machine vibration. In fact, the worst (in particular, noisiest) situation occurs when machine vibration interacts with, causing resonance of, floor 3. Locating accelerometer 16 close to a foot 4, i.e. close to the mechanical transmission element between casing 2 and floor 3, enables high-precision sensing by accelerometer 16 machine vibration transmission between casing 2 and floor 3.
In the Figure 1 embodiment, accelerometer 16 is fixed (preferably screwed) to casing 2 of washing machine 1, close to a foot 4.
In an alternative embodiment shown in Figure 2, accelerometer 16 is fixed (preferably screwed) to a foot 4 of casing 2.
In a further embodiment shown in Figure 3, accelerometer 16 is fixed to floor 3, close to a foot 4. In this case, accelerometer 16 is preferably fixed rigidly to floor 3, e.g. glued to floor 3 using bi-adhesive tape 17, and is preferably located under, for mechanical protection by, casing 2.
Washing machine 1 as described above has numerous advantages, by being easy to implement and highly effective and efficient in sensing machine vibration, on account of the position of accelerometer 16.
Though particularly advantageous for a washing machine, the above structure also applies to any other kind of laundry machine, such as a drier or a washer-drier.

Claims

A laundry machine (1) comprising:
a casing (2) resting on a floor (3) on a number of feet (4);

a revolving drum (5) supported by the casing (2);

a control unit (14) implementing a method of analysing machine vibration; and

at least one motion sensor (16) connected to the control unit (14);
the laundry machine (1) being characterized in that the motion sensor (16) is fixed to the floor (3) and located close to a foot (4).
A laundry machine (1) as claimed in Claim 1, wherein the motion sensor (16) is fixed rigidly to the floor (3).
A laundry machine (1) as claimed in Claim 2, wherein the motion sensor (16) is glued to the floor (3).
A laundry machine (1) as claimed in Claim 3, wherein the motion sensor (16) is glued to the floor (3) using bi-adhesive tape (17).
A laundry machine (1) as claimed in any of Claims 2 to 4, wherein the motion sensor (16) is located under the casing (2) for mechanical protection by the casing (2).
A laundry machine (1) as claimed in Claim 1, wherein the motion sensor (16) is an accelerometer.